Set Level - GE LBI31072 Phoenix Maintenance Manual

F
x
,t
i
A.
B.
A.
B.
STEP
2
:
USABI.I
SENS IT
IV ITY
(I2
DB
S
INAD}
If
STEP
1
checks
out properly,
neasure
the receir-er sensitivity as follows:
Applf-
a
1t-)00
rnicrovolt,
on-frequency
signal nodulated by
1000 Hz
with 3.0
kHz
deviation to
J601.
Place the
R\\GE
switch on the Disturtion
Ana11':er
in the
200
to
2000 Hz
distor-
tion
range
position
(1000 Hz filter
in
the circuit).
Tune
the filter for nini-
rnum
reading or
nu11 on
the lowest
pos-
sible scale (l00oo,30oo,
etc.)
Place the
R\)IGE
switch to tlie
SET
LEVEL
position (filter
out of the circuit)
and
adjust the input
LEVEL
control for
a +2 dB readi-ng on a
mi-d
range
(30%)
.
Set signal generator output to 0.4
uV.
Switch the RIIGE control from
SET
LEVEL
to the distorti-on range. Readjust
Dls-
tortion -\nal;-zer
SET LEVEL
as required
until a 12
dB
difference (+2
dB to
i10 dB) is obtained
between
the
SET
LEVEL
and
distortion
range
positions
(filter
out
and
fl1ter in)
.
I
The 12 dB
difference (Signal plus
Noise
and
Distortion to noise plus di-stortion
ratiol is the "usab1e" sensitivi-ty
1eve1.
The
sensitlvity
should be less
than
rateci 12 dB
SINAD
specifj-cations with
an audio
output of at least 1,5 l{atts
(0.56 Volts
Rit{S
across the 4.0 ohn re-
c-eiver load using the Distortion
Ana-
tyzer as a Voltneter)
.
l,eave
all controls as they are
and
all
equiprnent connected
if the
Modulation
Acceptance Bandwidth
test is to be
per-
forned.
SF,RVTCE
CHECK
1f the sensitivity
1eve1
is
more than
rated 12
dB SINAD, check the
alignment
of the
RF
stages as directed in
the
Alignment
Procedure,
STEP
3
MODULATION
ACCEPTANCE
BANDW
IDTH
(IF
BANDW IDTH)
If
STEPS
1
and
2
check
out properly,
neasure
the
bandwldth
as follows:
Set the Signal
Generator
output for
twice the microvolt reading obtained in
the 12
dB
SINAD
measurenent.
Set the
RANGE
control on the Distortion
Analyzer in the
SET LEVEI,
position
(1000 Hz filter out of the circuit),
and
adjust the input
LEVEL
control for
a
+?,
dB
reading on the
30%
range.
While increasing the deviation of
the
Signal Generator, switch the
MNGE con-
trol fron
SET LEVEL
to distortion
range
until a
1,2
dB
difference is
obtained
between
the
SET LEVEL
and
distortion
range readings (frorn +2 dB to -10
dB).
The
deviation control reading for
the
12 dB
difference is the
Modulation
Acceptance Bandwidth of the receiver.
I
t should be
more
than 17
kllz
.
SERVICE
CHECK
If the Modulation
Acceptance
Bandwidth
test
does not indicate the proper width,
refer to the
Recei-ver Troubleshooting
Procedure.
c.
D.
C.
D.
E.
F.